Massive DNS Issues on new client's servers

Computer Hardware & Server Infrastructure Builds
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Hey all! We (MSP) took over IT services from an internal guy at a local doctor’s office. 2 servers, 40 some computers. Pretty sizeable building. It was evident that the internal guy didn’t really know what he was doing… We had several computers that we could not put our RMM on due to lack of domain communication. So, we set our sights on fixing that. First, we redid the network. New switches, WiFi, fixed two network loops, DHCP scopes & IP conflicts all resolved - mainly caused by using Routers as APs. We rebooted everything after the network was redone, hoping to see better domain communication. No go, still issues. Here’s a small layout of their servers:

PDC: 2012 Standard server, holds all roles.
Data Server: 2019 Standard, on the domain, but does not communicate to the domain.

So, I spun up a 2016 VM on the 2019 server & put it on the domain. It will not let me promote to DC as it does not communicate to the VM. I begun looking into the DNS server on the 2012 server & poked around. It was evident that the server’s IP had been changed SEVERAL times. So, I begun cleaning up the DNS server’s entries of the old IPs, etc. Made it pretty similar to another 2012 Standard Server a client still has in use. Also used that server to cross reference some ADSI as we were told that the PDC may have been renamed at some point, although, I find no ADSI or DNS evidence of that.

My DNS settings are correct, have done this tons of times, have had senior engineers look it over, & even my father, who’s been a sys admin at a huge company for 20+ years. :frowning: We are all stumped. We are about to just spin up a new domain & do it all right.

Any ideas? Other than calling Microsoft? Haha.

Thanks in advance!

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This sounds eerily similar to an problem I had many years ago when migrating a very broken domain from Server 2000 environment to Server 2008 - I am wracking my brain trying to remember the fix - but I could not get DNS to play nice no matter what I did. I feel like it had something to do with the structure of how the PDC was looking at its own DNS - in that situation there were two DCs - so how they were looking at each other for DNS - it was one of those “I can’t believe I didn’t see this” things at 2am.

Sorry if this is not helpful - but I’ve done a few battles where IPv6 was enabled and causing havoc.

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It’s hard to know how to help, when the problem as described is kind of vague. “Does not communicate” - what do you mean, are DNS queries not working, are they literally not able to reach one another over the network (different subnets? Different net masks?)? What error(s) specifically are you getting? Is the only issue trying to promote a DC or are client workstations having problems too?

Also a little more information about the network would be useful like whether or not it is a flat network? Are all devices on the same switch? If it’s not flat, are VLANs used?

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